Grippers for handling preforms

ABSTRACT

Preform gripper comprising a handling arm ( 1 ) and a preform support plate ( 2 ) that has at an extremity thereof a semi-circular aperture ( 7 ) that is adapted to accommodate a cylindrical portion ( 28 ) of the collar of the preform. Hinged on said plate there are provided two parallel side gripping members ( 5, 6 ), two end portions of which ( 13, 14 ) are in the shape of an arc of a circle and are adapted to elastically move closer to each other up to a pre-established position. The gripper is adapted to, enable said cylindrical portion ( 28 ) of the collar of the preform to be fitted into and removed from, with a snap-like action, said semi-circular aperture ( 7 ) by pressing and pulling, respectively, the preform against two opposite, elastically enlargeable outer edges ( 31, 32 ) of said two side gripping members ( 5, 6 ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention refers to a gripper adapted to most effectively,and in a semi-automatic manner, seize, ie. hold firmly, and releasecylindrical bodies.

Although, for reasons of greater descriptive simplicity, reference willbe made to preforms of thermoplastic material used in the production ofcontainers in the following description, the present invention shall ofcourse to be understood as applying also to other cylindrical bodiesused in different applications, as far as they do not depart from thescope of the appended claims.

2. Description of Related Art

It is known, from DE 29713510 and FR 2720679, grippers for seizing andfirmly holding preforms comprise a handling arm, a pair of symmetrical,elastically diverging members, and connecting means between said arm andsaid symmetrical members. The latter are shaped so as to form aconcavity whose opposite arms are arranged and sized in such a manner asto enable a cylindrical portion of the collar of a preform to beinserted therein by means of a simple pressure of said collar againstthe outer portions of said concavity, which, owing to the action of sucha pressure, are caused to be enlarged by such an extent as adequate toenable the collar of the preform to slip into said concavity in which itis then retained.

However, such an operation and the particular type of gripper used tocarry it out, drawbacks as described below.

The preform may be subjected to both axial and transversal stresses. Inorder to be able to withstand such stresses., the symmetrical membersmust possess a considerable elastic strength.

However, the required extent of the elastic strength brings about aconsiderable friction between the arms and the outer surface of thepreform, which therefore undergoes a slight abrasion, considering thatit is made of thermoplastic material that is only slightly heated up. Ina situation of large-scale series production. The slight abrasions causetiny particles, ie. the so-called “flour” of the plastic materialinvolved to be produced, which contaminate the adjacent parts of theplant and disturb the regular flow of the subsequent process operationsthereby making them inaccurate.

If, on the other hand, such an undesired effect has to be reduced, theneed arises for the elastic gripping force of the arms to be reduced.Such a constraint, however, is largely known to all those skilled in theart to bring about corresponding inaccuracies in the positioning of thepreform, with clear handling difficulties resulting therefrom.

Moreover, making grippers provided with holding arms having aconsiderable elastic strength implies a production that requires a farhigher extent of accuracy and, therefore, is much more expensive.

BRIEF SUMMARY OF THE INVENTION

It is therefore a main purpose of the present invention to provide agripper for handling cylindrical bodies, and in particular plasticpreforms, which does away with the above described drawbacks and, at thesame time, is compact, safe and reliable in its operation, and requiresa simple, reliable construction based on the use of readily availabletechniques.

Such a type of gripper is obtained and implemented with thecharacteristics that are substantially described with particularreference to the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In any event, features and advantages of the present invention can morereadily be understood from the description that is given below by way ofnon-limiting example with reference to the accompanying drawings, inwhich:

FIG. 1 is a perspective view of a gripper according to the presentinvention;

FIG. 2 is a similar perspective view of a component part of the samegripper illustrated in FIG. 1;

FIG. 3 is a top plan view of the same component part illustrated in FIG.2;

FIG. 4 is a view along the A—A section of the component part illustratedin FIG. 3;

FIG. 5 is a view along the B—B section of the gripper illustrated inFIG. 1;

FIG. 6 is a view along the A—A section of the gripper illustrated inFIG. 5;

FIG. 7 is a perspective view of a partial assembly of some componentparts of the gripper illustrated in FIG. 1; and

FIG. 8 is a top plan view of the assembly illustrated in FIG. 7.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the above Figures, the gripper according to thepresent invention comprises a handling arm 1, a plate 2 for seizing andsupporting the preform 3, an interconnection means 4 provided betweenthe arm and the plate and firmly joined thereto, two symmetrical sidegripping members 5 and 6, and a cylindrical spring 8 provided in hole 33between corresponding extremities of the gripping members 5 and 6.

Plate 2 is provided, at an extremity thereof, with a semi-circularaperture 7 having a diameter adequate to accommodate a part of acylindrical portion 28 of the collar of preform 3.

It is, however, possible for the aperture to be given a non-circularshape, and, for example, alternatively have a non-circular shape, aslong as the aperture is capable of coupling with an adequate portion ofthe collar of the preform.

Plate 2 is furthermore provided, in correspondence of the opposite sideedges thereof, with two grooves 9 and 10 adapted to accommodate a sidegripping members 5 and 6, respectively.

Side gripping members 5 and 6 are hinged on interconnection means 4 bymeans of appropriate pivotally connecting means (pivots, pins and thelike). Since interconnecting means 4 is firmly joined with plate 2, sidegripping members 5 and 6 are substantially attached to plate 2. However,side gripping members 5 and 6 are able to slightly rotate with respectto plate 2 as a result of the pivotally connecting means engaging withappropriate holes 11 and 12 provided in side gripping members 5 and 6,respectively.

Side gripping members 5 and 6 are provided at extremities 13 and 14,respectively, located in correspondence with the semi-circular aperture7 having two arcs of a circle 15 and 16.

On the opposite side of extremities 13 and 14 there is provided acylindrical compression spring 8 which, as such, is biased to keep saidextremities 13 and 14 closed, or at least approached to each other.Extremities 13 and 14 have a limited separation gap because the innersides 17 and 18, respectively, of extremities 13 and 14 are adapted toabut against the outer edges of a central relief 20 of support plate 2,as illustrated in particular in FIGS. 1 and 5.

Side gripping members 5 and 6 are adapted to move into at least aresting position and at least a working position. The resting positionis determined by the action of spring 8 that tends to move extremities13 and 14 closer to each other up to the point at which the stoppingaction of central relief 20 comes into play.

In the resting position, arcs 15 and 16 move into an arrangement asillustrated symbolically in FIGS. 7 and 8, i.e. they outline a circlewhose diameter D is slightly smaller than the diameter H of thesemi-circular aperture 7, and the outer edges 21 and 22 of arcs 15 and16, respectively, are located at a distance M that is smaller than saiddiameter D and is also smaller than the outside diameter of the preform.

The working position is illustrated in FIGS. 1, 5 and 6. It can benoticed in the figures, that preform 3 is inserted within saidsemi-circular aperture 7, where it is retained by arcs 15 and 16 whichare pressed against cylindrical portion 28 of the collar of preform 3 bythe effect of the elastic action of the spring 8 and also owing to thefact that the diameter of the collar is greater than the diameter D ofarcs 15 and 16 of a circle in the resting position of semi-circularaperture 7. When preform 3 is so inserted, arcs 15 and 16 of a circleare deflected outwardly, thereby causing preform 3 to be firmly held.

In an advantageous manner, the preform retaining action can be furtherimproved if central relief 20 is provided, in correspondence of the edgethereof which is adjacent to semi-circular aperture 7, with abuttingmeans in the shape of an arc of circle 23, as illustrated in particularin FIG. 2, which is adapted to fittingly couple with cylindrical portionof the collar of preform 3, as illustrated in FIGS. 1, 5 and 6.

In this way, the combined effect of side members 5 and 6 elasticallyclosing and abutting means 23 moving to couple against the collar ofpreform 3 causes the latter to be firmly held, in an elasticallyreleasable manner, against the described gripper.

It is in fact sufficient for an appropriate portion of the collar ofpreform 3 to be pressed in an axial direction into semi-circularaperture 7 in order to cause side gripping members 5 and 6 to move apartby an adequate extent, thereby allowing for preform 3 to slide intosemi-circular aperture 7. When side gripping members 5 and 6 are then somoved into such a position, they tend to return to their restingposition, owing to the action of spring 8, thereby causing the collar ofpreform 3 to be firmly held.

To sum up, the grippers for use with preforms having a collar portion,according to the invention include a handling arm 1, means 2 adapted tosupport and handle the preform 3, interconnection means 4 providedbetween arm 1 and means 2 and firmly joined thereto, support means 2 isformed by a plate made in a single integral piece that is provided, atan extremity thereof, with a preferably semi-circular aperture 7 adaptedto move into coupling with and accommodate a portion 28 of the collar ofthe preform 3. The grippers further include two preferably symmetrical,parallel side gripping members 5 and 6 hinged on to the plate, whose twoextremities 13 and 14, respectively, are formed with contours 15 and 16,respectively, adapted to be capable to move into a fitting coupling withtwo respective portions of the collar of preform 3, and are furtheradapted to elastically move closer to each other up to a pre-determinedposition.

It should be particularly noticed that, with such an embodiment, theside stresses on the preform are easily neutralized by the resistance ofthe arms of semi-circular aperture 7, without any consequence on thecapability thereof to grip and hold preform 3 in a firm and efficientmanner. On the other hand, the axial stresses determined by preform 3being inserted in and released from the gripper may be limited to anydesired extent by simply adjusting the characteristics of the spring 8accordingly, without impairing the stability in any way and, above all,the precision of the position in which preform 3 is held, owing to theeffect of the abutting means 23 getting so coupled.

A further improvement in the way in which the preform is inserted iseasily obtained if two side gripping members 5 and 6 are provided, atextremities 13 and 14, respectively, with edges 31 and 32, respectively,having appropriate flared shapes and arranged so as to define a V-shapedor funnel-shaped configuration in view of facilitating preform 3 to moveinto self-positioning and in view of facilitating extremities 13 and 14to move apart under the action of even a moderate axial pressure exertedby the preform.

It shall be appreciated that the description and illustrations givenabove with reference to the accompanying drawings have been given as amere example of the present invention, and that a number of variants andmodifications can therefore introduced thereto without departing fromthe scope of the present invention.

What is claimed is:
 1. A gripping device operable to grip a preform having a collar portion, said gripping device comprising: a handling arm; support means adapted to support and handle the preform, formed by a plate made in a single integral piece that is provided at an extremity thereof with a semi-circular aperture adapted to move into coupling with and accommodate a cylindrical portion of the collar of the preform; interconnection means provided between said arm and said support means and firmly joined thereto; two symmetrical, parallel side gripping members hinged onto said plate, whose two extremities are formed with respective contours adapted to be capable to move into fittingly coupling with two respective portions of the collar of the preform, and are further adapted to elastically move closer to each other up to a pre-determined position; one or more elastic members that operate in a compressing mode on said two side gripping members on the opposite side of said respective extremities, wherein said elastic members comprise a cylindrical spring operable to provide a force between said elastic members, wherein said plate is provided, on the opposite side of said extremities, with a hole adapted to accommodate said spring, characterized in that said plate is provided centrally with a relief portion, a resting position of said side gripping members being abutting against respective grooves of said relief portion.
 2. A gripping device according to claim 1, wherein said relief portion is provided, on the edge thereof which is adjacent to said aperture with a step-like abutment that is adapted to fittingly couple with said cylindrical portion of the collar of the preform.
 3. The gripping device according to claim 1, wherein said two side gripping members are provided with respective outer edges that are so oriented as to be able to define a funnel-shaped or V-shaped configuration adapted to facilitate the insertion of said cylindrical portion of the collar of said preform.
 4. The gripping device according to claim 3, wherein said relief portion is provided, on the edge thereof which is adjacent to said aperture, with a step-like abutment that is adapted to fittingly couple with said cylindrical portion of the collar of the preform.
 5. The gripping device according to claim 1, characterized in that it is adapted to enable said cylindrical portion of the collar of the preform to be fitted into and removed from said aperture, with a snap-like action, by simply pressing and pulling, respectively, said cylindrical portion against outer edges capable of widening elastically of said two side gripping members.
 6. A gripping device operable to grip a preform having a collar portion, said gripping device comprising: a handling arm; a support plate having an aperture formed at an extremity thereof, the aperture having a shape capable of accommodating a first portion of the collar; an inner connecting device connecting said handling arm to said support plate; a gripping member having a pivot point and an extremity that is shaped to conform with a contour of a second portion of the collar, said gripping member being pivotally attached to said support plate at the pivot point, said gripping member being operable pivot about the pivot point such that said extremity moves between a first position and a second position; and a biasing device operable to provide a biasing moment to said gripping member such that said extremity is biased in a direction toward the second position, wherein said biasing device is disposed at a position such that the pivot point of said gripping member is positioned between said biasing device and said extremity, wherein said support plate comprises a relief portion having a groove, and wherein said relief portion is disposed such that said gripping member, at the second position, abuts against the groove.
 7. The gripping device according to claim 6, wherein said relief portion comprises an abutment disposed adjacent to the aperture. 